Transceive Beamforming in FDA-MIMO-Based Dual-Function Radar-Communication Systems for Low Probability of Interception

Low probability of interception (LPI) technology is critical for the self-protection of dual-function radar-communication (DFRC) systems in hostile environments. However, the range-dimensional uncontrollability of the beampattern imposes a bottleneck limitation on LPI development. This paper investigates a transceive beamforming for frequency diverse array (FDA)-multiple-input multiple-output (MIMO)-based DFRC systems. Initially, we innovatively construct the signal model for the FDA-MIMO DFRC system, which surmounts the inseparability between frequency offsets and transmitting antennas. Subsequently, the equivalent transmitted beampattern and communication channel are derived into two-dimensional range-angle expressions, aiming to implement joint range-angle beamforming. The communication symbols are strategically placed in predetermined range-angle positions of each user through the beampattern modulation technique. The LPI optimization problem is formulated as the minimization of transmitting beamforming power, subject to the constraints of radar SINR and communication sum-rate. To tackle the non-convex problem with high-dimensional nonlinear constraints, a distributed alternating algorithm is developed for fast solving, involving sequence convex approximation (SCA), weighted mean-square error minimization (WMMSE), and alternating direction method of multipliers (ADMM). Simulation results demonstrate that our method achieves punctate multi-target detection and multi-user communication in two-dimensional range-angle planes, enormously facilitating the LPI capability.